It all started some time ago, first the engine was starting and stalling after fraction of a second. But if the pedal was pushed - engine was running. By the way - interesting thing - the AT gearbox was not working then. Might be not connected, but I am not sure. Only when push acc pedal to the bottom the slight torque occurred. Anyway. First thing I was going to replace idle air valve, simple stepper motor with rubber cap. Got it new, from eBay (~45 USD). Replaced, but the idle RPM is pulsating, in specific conditions very strong. Take a look at the Youtube:


At this time the reverse gear is turned on, AC turned off but compressor working because I put the regulator front window defogger position, headlamps on. So, seems to be normal load on the engine, but the RPM drops way too low and goes back to normal. Under no load engine is running fine, under small load pulsation is also small.
Ok I admit, I took the car to the workshop, before I did the diagnosis myself (and before I found the faulty idle valve) and I know they put their dirty fingers on the idle RPM regulation bolt. Damn I hate them. I somehow managed to regulate the idle RPM bolt, but I am not sure if I did it right. Anyway, the stepper is working (OBD tester shows its opening and closing). So I might need to retune the bolt position. But if not - what did I missed ? The faulty stepper had one winding burned and shorted circuit - can if affect the control unit and burn the winding controller ? I will check that with oscilloscope, but anyway, your advices are welcome.

 

Try cleaning the throttle body. If it's gummed up, it may be affecting the idle air control.

 

Wow, cant believe this post is so old. Times goes by so fast... Anyway, I still have the coupe And now I can continue the story of sadomasochism of being its owner By the way, nice to see some old nicks, dcotter and other guys, how are you holding on there ? Ok, so, I replaced the idle air motor, but it was not working correctly. Had tu adjust the idle air bolt, but it was broken even before I purchased the vehicle, so made a new one, from bronze. With Tactrix Openport cable (made by myself) managed to put the engine into service mode to tune the bolt position. But still had the issue with unstable RPM. Checked the idle air motor, should be working, but its power supply seemed strange. As it is regular stepper motor, it is powered by a special signal with special pattern. Well, the pattern was missing. As all the control of IAM is done by ECU, once again, had to disassemble some plastics to get to it. There is one chip, SPF5002A, a stepper motor controller. Purchased couple of them from AliExpress, resoldered the new and now RPMs are not pulsing. So, the reason was burned chip... Seems easy when you know where to look...